Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04M—TELEPHONIC COMMUNICATION
  • H04M7/00—Arrangements for interconnection between switching centres
  • H04M7/006—Networks other than PSTN/ISDN providing telephone service, e.g. Voice over Internet Protocol (VoIP), including next generation networks with a packet-switched transport layer
  • H04M7/0066—Details of access arrangements to the networks
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04M—TELEPHONIC COMMUNICATION
  • H04M3/00—Automatic or semi-automatic exchanges
  • H04M3/42—Systems providing special services or facilities to subscribers
  • H04M3/42314—Systems providing special services or facilities to subscribers in private branch exchanges
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04M—TELEPHONIC COMMUNICATION
  • H04M7/00—Arrangements for interconnection between switching centres
  • H04M7/006—Networks other than PSTN/ISDN providing telephone service, e.g. Voice over Internet Protocol (VoIP), including next generation networks with a packet-switched transport layer
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W36/00—Hand-off or reselection arrangements
  • H04W36/16—Performing reselection for specific purposes
  • H04W36/18—Performing reselection for specific purposes for allowing seamless reselection, e.g. soft reselection
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
  • H04W88/08—Access point devices

Definitions

• end devices that have different purposes, such as can increasingly be used to transmit voice, video, fax, multimedia, information, text, program and / or measurement data, wirelessly coupled.
• a connection to such mobile end devices is usually established via so-called base stations coupled to a communication network, which can connect to the mobile end devices via an air interface.
• base stations coupled to a communication network, which can connect to the mobile end devices via an air interface.
• mobile terminals are also understood to mean so-called cordless terminals.
• An exchange of user data via the air interface between a mobile terminal and a base station generally takes place within time frames specified by a time cycle, which are also referred to below as radio time frames.
• the area around a base station in which a wireless connection of predetermined quality can be established between a mobile terminal and this base station is also referred to as the radio cell of this base station.
• several base stations are generally distributed over the area to be supplied in such a way that their radio cells form a nationwide radio network.
• a mobile terminal registered in such a radio network can switch between the base stations of this radio network that are in radio range.
• the "handing over" of a mobile terminal from a first base station to a second base station with an existing connection is also referred to as "handover".
• handover As a rule, such a change in the course of the connection should be carried out without any noticeable interruption of the binding. In this case one speaks of a "seamless handover".
• Air interface are synchronized with each other. For example, user data to be transmitted via a DECT air interface are embedded in radio time frames, the start of which may differ from one another by a maximum of 2 ⁇ s in the base stations involved in a “seamless handover”.
• a synchronization of base stations is to be understood in particular as a synchronization of radio time frames on the basis of a user data exchange with mobile terminals of different base stations.
• a mobile communication system is known from the published patent application WO 96/38990, in which base stations are each connected to a private branch exchange via an So interface in accordance with the ISDN standard.
• a reference clock from the private branch exchange is transmitted to the base stations via the So interface on the physical layer of the transmission protocol used.
• the clock generators of these base stations are synchronized on the basis of the reference clock received equally from all base stations.
• the base stations are provided with time information via a local network, e.g. transmitted by a time information server. Since the base stations each align their own time measure with received time information, these base stations are synchronized with one another.
• the local area network which is often also referred to as LAN, can be implemented in a variety of ways, such as, for example, “Ethernet”, “Token Ring”, “Token Bus” or “FDDI”.
• the invention allows base stations to be synchronized with little effort even in complex mobile communication networks.
• base stations can be easily integrated into local computer networks, and an existing network infrastructure can be used for synchronization.
• a connection of base stations of a mobile communication network to a local network is particularly advantageous also with regard to an increasing integration of voice and data communication.
• An essential aspect of the invention is the fact that a transmission of time information via a local network is particularly well suited for the synchronization of base stations for the purpose of a "seamless handover".
• the invention can now be used to achieve a high level of synchronization accuracy, especially in the case of adjacent base stations, since in the case of adjacent base stations both the transit times of time information for the respective base station and the transit time fluctuations differ only slightly.
• the time clock of a base station can be adjusted by readjusting its clock frequency and / or phase position.
• a corresponding control signal can be fed to the time clock via an integrating element.
• a malfunction of the timer can also be corrected by inserting or omitting clock cycles.
• time information can be requested by a base station via the local network from a time information server.
• the request can preferably be made via known network protocols, e.g. the so-called “Network Time Protocol” (NTP) or the so-called “Digital Time Synchronization Protocol” (DTSS).
• NTP Network Time Protocol
• DTSS Digital Time Synchronization Protocol
• the time difference between requesting and receiving time information can be measured in order to determine an estimated value for the runtime of the time information from the time information server to the relevant base station.
• the time clock of the base station can be synchronized with the clock of the data stream transmitter on average over time.
• a clock frequency control signal derived from the fill level can be fed to the time clock via an integrating element.
• a data stream of communication data received via the local network and to be sent to a mobile terminal such as e.g. Voice data. Since communication data and, in particular, voice data are often transmitted at an existing connection at a precisely adhered to, based on the timing of the transmitter of the communication data transmission rate, the clock frequency of the clock can be stabilized particularly precisely on the basis of received communication or voice data.
• FIG. 1 shows a mobile communication network with two base stations coupled to a switching device via a local network
• Figure 2 shows a more detailed representation of one of the base stations connected to the local network.
• FIG. 1 shows a mobile communication network with a switching device VE connected to a fixed network FN and two base stations BS1 and BS2 coupled to the switching device VE via a local area network LAN.
• the base stations BS1 and BS2 are implemented in the present exemplary embodiment as DECT base stations (digital European cordless telephone). While over ⁇ ⁇ > N3 P 1 P 1 no cn O C ⁇ o Cn
• the communication data KD1, KD2 sent by the switching device VE at a constant data rate are used by the base stations BS1, BS2 to stabilize the clock frequency of their respective time clock ZTG during the time intervals between individual queries of time information.
• the current fill level of the input buffer memory EP ie the limit up to which the input buffer memory EP is filled with communication data KD1 is recorded in the base station BS1 at regular time intervals and transmitted in the form of fill level information FI to the frequency control FS.
• the frequency control FS forms a frequency control signal FRS, which is output via an integrating element IG and is combined with the frequency control signal formed by the timing clock device ZJ for regulating the clock frequency of the timing clock ZTG.
• the time constant of the integrator IG of the frequency control FS is dimensioned such that runtime fluctuations of the communication data KD1 typically occurring in the local network LAN are compensated for.
• the integrators IG of the frequency control FS or the timing adjustment device ZJ can be implemented, for example, with the aid of a digital circuit to form moving averages.
• a frequency control signal FRS is generated by the frequency control FS to increase the clock frequency of the timing generator ZTG, while if the fill level is below average ⁇ ⁇ f-0 ro P- P 1
• the number of network elements connected between the switching device VE and the respective base station BS1 or BS2 and the number of network elements connected between the base stations BS1 and BS2 does not exceed a predetermined number.

Landscapes

• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)
• Small-Scale Networks (AREA)
• Synchronisation In Digital Transmission Systems (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=7921831

Family Applications (1)

Country Status (7)

Cited By (4)

Families Citing this family (26)

Citations (3)

Family Cites Families (4)

• 2000
  • 2000-07-17 DE DE10034686A patent/DE10034686A1/de not_active Withdrawn
  • 2000-09-07 WO PCT/DE2000/003106 patent/WO2001020889A1/de active IP Right Grant
  • 2000-09-07 CA CA002384688A patent/CA2384688C/en not_active Expired - Fee Related
  • 2000-09-07 CN CNB008128464A patent/CN1211953C/zh not_active Expired - Fee Related
  • 2000-09-07 DE DE50011702T patent/DE50011702D1/de not_active Expired - Lifetime
  • 2000-09-07 JP JP2001524342A patent/JP3757167B2/ja not_active Expired - Fee Related
  • 2000-09-07 US US10/088,131 patent/US7190703B1/en not_active Expired - Lifetime
  • 2000-09-07 EP EP00974300A patent/EP1212889B1/de not_active Expired - Lifetime
  • 2000-09-12 DE DE50007000T patent/DE50007000D1/de not_active Expired - Lifetime

Patent Citations (3)

Also Published As

Similar Documents

Legal Events